This application claims priority from Japanese Patent Application Reference No. 11-075174 filed Mar. 19, 1999, the entire contents of which is incorporated herein by reference for all purposes.
The present invention relates generally to computing systems and more specifically to techniques for controlling copying of logical volumes within a computer storage system.
Modern computing systems can comprise a plurality of logical volumes within a mass storage system. Mass storage systems can be implemented in a variety of form factors, including DASD, optical storage media, tape storage media, and the like. Often, it is desirable to perform copies of content from one logical volume to another logical volume in a mass storage system. A conventional method for performing such a copy is known as a REMOTE COPY function. In the REMOTE COPY function, host channels are used for transferring the copied data. A control unit, behaving as if it were a processing unit, sends data stored in a logical volume via a host channel. The data is received by another host channel and written to the logical volume. Thus, a copy of the logical volume is created.
When the copy function is executed in one control unit, a plurality of host channels is employed. Therefore, the number of host channels available for the normal host connection is decreased. Such conventional methods typically burden computational resources, such as host channels, during the copy process.
What is really needed are techniques for copying information from one logical volume to another without burdening host channel resources for connecting between the control unit and processing units.
According to the present invention, techniques for controlling copying of logical volumes within a computer storage system are provided. A representative embodiment includes a plurality of storage devices controlled by a control unit, one or more processors, and a buffer memory for temporarily storing data read from the storage devices within the control unit. The storage devices can be addressed as logical volumes.
In an exemplary embodiment, the invention provides a method for creating a copy on a second logical volume of data stored on a first logical volume. The method can comprise a variety of steps, such as specifying a relationship between two or more logical volumes. The method can also include creating a copy of data in a specified first logical volume into said second logical volume. Creating such a copy can include steps of copying data from the first logical volume to a first location in a buffer memory located within a control unit. Copying can be performed by the control unit substantially independently of processor control. Then, data can be copied from the first location in the buffer memory to a second location in the buffer memory. Subsequently, data from the second location in the buffer memory can be copied to the second logical volume. This copying can be performed by the control unit substantially independently of processor control, also. As used herein, substantially independently of processor control can include performing copy processing at the control unit level without necessitating intermediate communication between a command start from the processor to the control unit and a command complete signal from the control unit to the processor.
In another embodiment, the invention provides a computer system comprising a plurality of devices. A plurality of storage devices controlled by one or more control units can be part of the computer system. One or more processing units operable to access the control unit or units can also exist in the computer system. A buffer memory operable to temporarily store data read from the storage devices within the control unit can also be part of the computing system. The storage devices can be addressed as one or more logical volumes. The control unit is able to establish a relationship between at least two logical volumes (i.e., a first logical volume and a second logical volume) located in the storage devices. The control unit can create a copy of data in the first logical volume into the second logical volume. Such creating a copy can include copying data from the first logical volume to a first location in the buffer memory. Then, the data can be copied from the first location in the buffer memory to a second location in the buffer memory, changing meta-data indicating the device that may access the data to reflect the second logical volume. Thereupon, the data can be copied from the second location in the buffer memory to the second logical volume. These operations by the control unit can be performed substantially independently of the processing units. In a representative embodiment, the buffer can comprise approximately 10 Gigabytes, for example.
In a further embodiment, the invention provides a computer program product for controlling the copying of information from a first logical volume to a second logical volume in a computer system. The computer program product can comprise a computer readable storage medium containing a variety of program code. Code for specifying a relationship between the first logical volume and the second logical volume can be part of the computer program product. The product can also include code for creating a copy of data in the first logical volume into the second logical volume. The code for creating a copy can comprise various program codes. Program code for copying data from the first logical volume to a first location in a buffer memory can be part of the program product. The product can also include code for copying the data from the first location in the buffer memory to a second location in the buffer memory. Code for copying the data from the second location in the buffer memory to the second logical volume can also part of the program product. The codes for copying the data from the first location in the buffer memory to the second location in the buffer memory is executed by a control unit substantially independently of a central processing unit.
Select embodiments according to the present invention can be operable with an arrayed disk subsystem. Data may be readily moved to a logical volume having different access characteristics by creating a pair among logical volumes having different RAID levels. Specific embodiments according to the present invention can include a function for creating the data copy, such that, a single logical volume is defined as a primary volume, plural different logical volumes are defined as secondary volumes, and each pair is defined as a different pair.
Numerous benefits are achieved by way of the present invention over conventional techniques. Some embodiments according to the present invention can create a copy of specified logical volume without occupying host channels. In such embodiments, control unit load can be reduced. Many embodiments according to the present invention can create a copy at a specified time. Further, in specific embodiments, data in a secondary volume can be used as a series of the historical records of the primary volume switching the secondary volumes one after another. Many embodiments enable data to be replicated more easily, quickly and with improved system loading than heretofore known methods. These and other benefits are described throughout the present specification. A further understanding of the nature and advantages of the invention herein may be realized by reference to the remaining portions of the specification and the attached drawings.